Ringing Suppression in a Controller Area Network With Flexible Data Rate Using Impedance Switching and a Limiter

The ringing and the resulting asymmetry in the propagation delay are the main causes of bandwidth degradation and communication errors in a controller area network (CAN) with flexible data rate. Therefore, in this paper, the mechanism of ringing is analyzed, and the ringing suppression circuit is proposed based on the analysis. The proposed circuit includes an impedance matching resistor and a forward-biased diode for terminating the repetition of reflections and limiting the magnitude of the ringing. These components are temporarily connected by operating a switch that is controlled by the TxD signal of a CAN controller so that the ringing suppression circuit only engages when necessary and at the correct time. The performance of the ringing suppression circuit is verified by experiments. The experimental results show that the proposed circuit keeps the ringing adequately suppressed and the good symmetry in the propagation delay across the physical bus is possessed.